Field-emission properties of carbon nanotubes grown using Cu-Cr catalysts

In addition to Ni, Co, and Fe, the authors show that a copper (Cu) chromium (Cr) alloy can be a good catalyst for controlled growth of carbon nanotubes (CNTs). A thermal chemical vapor deposition was used at 600 degrees C to deposit the CNTs, and a dual-target magnetron sputtering system was used to control the ratio of the Cu/Cr alloy. The material properties of the CNTs, such as concentration, diameter, and density, are directly affected by the ratio of Cu/Cr alloy, which subsequently affect the field-emission properties. Their results showed that Cr can be used to effectively control the catalytic effects of the Cu catalysts, where the quality of the CNTs could vary while the density could be controlled from 4 X 10(7) to 5 X 10(10) tubes/cm(2). The field-emission current density of the CNT film increases with Cu/Cr ratio from 1/6.4 to 4.6/1 and decreases when the Cu/Cr ratio is more than 4.8/1 in the alloy film. When the Cu/Cr ratio is at 4.6/1, the average current density peaks at 5129 mu A/cm(2) at the applied field of 3.53 V/mu m, showing an optimized field-emission property. (C) 2009 American Vacuum Society. [DOI: 10.1116/1.3039691]